Modulating the activity of neurons in the brain is critical for normal synaptic transmission. In certain disease states, hyperactivity of neurons can lead to neuronal death. The novel protein that is the subject of this proposal is MONaKA (Modulator of Na,K-ATPase). The Na,K-ATPase is a critical protein for reestablishing the electrochemical gradient of neurons. Pharmacological blockade of the Na,K-ATPase can lead to neuronal death. MONaKA was first discovered as a modulator of the plasma membrane Na,K-ATPase. MONaKA binds to the [unreadable] subunit of the Na,K-ATPase and via this interaction, decreases the function of the a subunit. This is a unique discovery because most modulators of the Na,K-ATPase bind to the a subunit. Recently, I discovered that MONaKA binds to and modulates the Na+-dependent glutamate transporter, GLT-1. GLT-1 is primarily found on astrocytes and accounts for greater than 90% of synaptic glutamate removal in the mammalian forebrain. Maintaining extracellular levels of glutamate below neurotoxic levels is important for preventing neuronal death. Thus, the fact that MONaKA is able to bind and modulate this critical glutamate transporter is a novel and exciting discovery. Interestingly, GLT-1 also binds to the [unreadable] subunit of the Na,K- ATPase. This grant will explore MONaKA's modulation of GLT-1 and the [unreadable] subunit using electrophysiological techniques, as well as molecular mutagenesis to disrupt binding of all three proteins. The combined results from this proposal will determine the modulatory role of MONaKA on GLT-1 and Na,K-ATPase. These experiments will establish the foundation for exploring the in vivo role of MONaKA in normal and neuropathological synaptic transmission. PUBLIC HEALTH RELEVANCE: MONaKA (Modulator of Na,K-ATPase) is a novel protein that may modulate synaptic transmission in the central nervous system (CNS). It binds to and modulates two proteins important for neuronal activity, a glial glutamate transporter and the Na,K-ATPase. Because the CNS is a delicate balance of activity, studying a protein that modulates two critical proteins whose function are essential for neuronal activity is important in understanding and preventing neuronal death.